Add "Sticky Kiosk" setting that stores "Kiosk" mode when activate

- This setting is important to allow creation ofa Home Screen app on iOS/iPadOS
- If kiosk mode is accidentally made sticky, it can be cleared by adding '&kiosk=false` to the URL
- Ctrl-K will now also exit kiosk mode

This adds a `stickyRead` parameter to settings, that means "read it if it's there, but don't write it"

server/scripts/index.mjs

@@ -349,10 +349,20 @@ const updateFullScreenNavigate = () => {
 };
 
 const documentKeydown = (e) => {
-	// don't trigger on ctrl/alt/shift modified key
-	if (e.altKey || e.ctrlKey || e.shiftKey) return false;
 	const { key } = e;
 
+	// Handle Ctrl+K to exit kiosk mode (even when other modifiers would normally be ignored)
+	if (e.ctrlKey && (key === 'k' || key === 'K')) {
+		e.preventDefault();
+		if (settings.kiosk?.value) {
+			settings.kiosk.value = false;
+		}
+		return false;
+	}
+
+	// don't trigger on ctrl/alt/shift modified key for other shortcuts
+	if (e.altKey || e.ctrlKey || e.shiftKey) return false;
+
 	if (document.fullscreenElement || document.activeElement === document.body) {
 		switch (key) {
 			case ' ': // Space